This paper investigates the downlink system level performance for Layer-3 (L3) and Layer-1 (L1) relays with orthogonal frequency division multiple access (OFDMA) used in LTE-Advanced. Various practical factors are taken into account in the evaluations such as the processing delay and upper-bound of the amplifier gain of the L1 relay, capacity limitation of the backhaul channels, and empty buffer status at the L3 relay. Based on system-level simulations, we clarify the system impact of several conditions for the relay such as a relay location, the number of relay nodes, the number of backhaul (radio link between eNode B and L3 relay) subframes, and investigate the throughput performance gain of the Release 10 LTE L3 relay compared to the L1 relay.